This invention relates to guiding means used to guide intraluminal devices through body lumens and particularly to guidewires used to advance catheters within body lumens in procedures such as percutaneous transluminal coronary angioplasty (PTCA).
In typical PTCA procedures a guiding catheter having a preformed distal tip is first percutaneously introduced into the vascular system of a patient using a Seldinger technique. The guiding catheter is then advanced through the peripheral vasculature until the distal end thereof reaches the ostium of the coronary artery most accessible to the artery to be dilated. The guiding catheter may then be torqued at the proximal end in order to seat the distal end of the guiding catheter in the ostium of the artery.
A balloon catheter assembly is formed by loading a guidewire through the inner lumen of a balloon dilatation catheter such that the distal tip of the guidewire extends out of the distal tip of the balloon catheter. The balloon catheter assembly is connected to an adapter at its proximal end; thereafter its distal end is inserted into the proximal opening of the guiding catheter and advanced therethrough until the distal tip of the balloon catheter assembly reaches the distal end of the seated guiding catheter. The guidewire is then advanced out of the distal end of the balloon catheter and through the coronary artery until the distal tip of the guidewire extends distally several centimeters of the lesion to be dilated, thus providing support to the dilatation catheter during the angioplasty procedure. Thereafter, the balloon catheter is advanced out of the distal end of the guiding catheter over the guidewire until it reaches a desired location within the artery to be dilated, e.g., when the balloon portion of the catheter traverses the stenotic lesion to be dilated.
Under model conditions, once the balloon catheter and guidewire have been properly positioned across a lesion, the balloon is inflated to compress the atherosclerotic plaque against the inside of the artery wall and to otherwise expand the inner lumen of the artery. The balloon is then deflated so that blood flow is resumed through the now dilated artery and the dilatation catheter assembly and guiding catheter are removed.
Conventional guidewires for angioplasty and other intravascular procedures are typically comprised of an elongated core member, with one or more tapered sections near the distal end; a helical coil which is disposed about the distal portion of the core member; and a shapable ribbon which extends within the flexible body and which is secured to the distal end of the helical coil by suitable means such as welding to form a rounded plug. A knob or handle may be provided on the proximal end of the core member to rotate and thereby steer the guidewire which is being advanced through a patient's vasculature. The shapable ribbon may either be formed by flattening the distal extremity of the core member or by attaching a separate ribbon which is secured to the distal extremity of the core member.
Further details of dilatation catheters, guidewires, and devices associated therewith for angioplasty procedures may be found in U.S. Pat. No. 4,323,071 (Simpson-Robert), U.S. Pat. No. 4,439,185 (Lundquist), U.S. Pat. No. 4,516,972 (Samson), U.S. Pat. No. 4,538,622 (Samson et al.), U.S. Pat. No. 4,554,929 (Samson et al.), U.S. Pat. No. 4,582,181 (now Re 33,166) (Samson), U.S. Pat. No. 4,616,652 (Simpson), U.S. Pat. No. 4,638,805 (Powell) and U.S. Pat. No. 4,748,982 (Horzewski et al.) which are hereby incorporated herein in their entirety by reference thereto.
It is not uncommon during an angioplasty procedure for the physician to be unable to cross a stenosis with the guidewire that was advanced through the patient's vasculature. In that event, the guidewire is usually removed and another guidewire with a stiffer distal tip is advanced through the patient's vasculature so that it can be pushed across the lesion. Frequently, however, the guidewire with the stiffer distal tip cannot be advanced through the patient's tortuous vasculature to the desired location without causing trauma to the vasculature.
Heretofore, physicians have been forced to select guidewires which either have increased pushability and decreased flexibility or guidewires with increased flexibility and decreased pushability. As a result of these selection constraints, physicians will typically attempt to anticipate the stiffness which will be needed to cross the stenosis to be dilated while avoiding a guidewire which may unduly increase the risk of vascular trauma to the patient. The difficulty with this trial and error method of selecting guidewires is that if the physician selects a guidewire with inappropriate characteristics, additional time must be spent removing the guidewire and inserting another more appropriate guidewire.
What has been needed and heretofore unavailable is a guidewire which has the flexible and steerable characteristics which enable the guidewire to traverse the patient's peripheral and coronary vasculature with little or no trauma, but which has means to increase the stiffness of the distal tip in order to facilitate crossing an occlusion.